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We have been following a slew of defamation lawsuits by political figures over the last few years. (See, e.g., here and here and here and here and here and here and here and here). For torts scholars, it has been a bonanza of interesting issues touching on every element of defamation law. There is now an important ruling out of the United States Court of Appeals for the Eighth Circuit that could have enormous implications not just for the media but anyone who retweets stories or claims. The appellate panel ruled unanimously for Rep. Devin Nunes against journalist Ryan Lizza...

A recent study, published in the Astrophysical Journal, offers potential explanations for the appearance of a green blob near the galaxy's center, which appeared and disappeared within weeks. The main goal of the NuSTAR observations was to examine a supernova -- a huge star explosion. The green blob, known as an ultraluminous X-ray source (ULX...didn't appear during the first observation, but showed up during a second one 10 days later. Another space telescope, NASA's Chandra X-ray Observatory, then looked again and found the object, ULX-4, had quickly disappeared. "Ten days is a really short amount of time for such a...

Stars the mass of our Sun, and up to eight times more massive, evolve into red giants towards the end of their lives. Their outer layers puff up and expand millions of kilometres, their dusty, gassy shells blown away from the central star in relatively slow winds up to few hundreds of km/s. Even larger stars, up to 25–30 times more massive than the Sun, race through their fuel and explode in a supernova, sometimes leaving behind a spinning stellar corpse with a strong magnetic field, known as a neutron star. This tiny core packs the mass of nearly one...

Explanation: Why are the regions above sunspots so hot? Sunspots themselves are a bit cooler than the surrounding solar surface because the magnetic fields that create them reduce convective heating. It is therefore unusual that regions overhead -- even much higher up in the Sun's corona -- can be hundreds of times hotter. To help find the cause, NASA directed the Earth-orbiting Nuclear Spectroscopic Telescope Array (NuSTAR) satellite to point its very sensitive X-ray telescope at the Sun. Featured above is the Sun in ultraviolet light, shown in a red hue as taken by the orbiting Solar Dynamics Observatory (SDO)....

In just a matter of days, the corona — a cloud of particles traveling near the speed of light — fell in toward the black hole. The observations are a powerful test of Einstein’s theory of general relativity, which says gravity can bend space-time, the fabric that shapes our universe, and the light that travels through it. “The corona recently collapsed in toward the black hole, with the result that the black hole’s intense gravity pulled all the light down onto its surrounding disk, where material is spiraling inward,” said coauthor Michael Parker from the Institute of Astronomy ... NuSTAR...

Explanation: How fast can a black hole spin? If any object made of regular matter spins too fast -- it breaks apart. But a black hole might not be able to break apart -- and its maximum spin rate is really unknown. Theorists usually model rapidly rotating black holes with the Kerr solution to Einstein's General Theory of Relativity, which predicts several amazing and unusual things. Perhaps its most easily testable prediction, though, is that matter entering a maximally rotating black hole should be last seen orbiting at near the speed of light, as seen from far away. This prediction...

Explanation: The aftermath of a cosmic cataclysm, supernova remnant Cassiopeia A (Cas A) is a comfortable 11,000 light-years away. Light from the Cas A supernova, the death explosion of a massive star, first reached Earth just 330 years ago. Still expanding, the explosion's debris cloud spans about 15 light-years near the center of this composite image. The scene combines color data of the starry field and fainter filaments of material at optical energies with image data from the orbiting NuSTAR X-ray telescope. Mapped to false colors, the X-ray data in blue hues trace the fragmented outer ring of the expanding...